This application relates to motorized window shades and more specifically relates to an ultraquiet motorized window shade employing a microprocessor controlled motor which is separable from the shade roller and which has electrostatic discharge (ESD) protection for the control circuit.
Motorized roller shade assemblies are well known in which a shade can be reeled onto and off of an elongated roller under the control of an electrical motor. Such shades can then be operated remotely to control the amount of light entering a room, to control the temperature and/or air flow in a room, to provide ultraviolet protection, and to provide privacy. The motor may be controlled by a microprocessor. a hand held infrared (IR) remote control, or a remote wall switch to control the direction and speed of rotation of the roller, preset stop positions, and the like. Further, controls driven by time clocks, photo sensors, occupancy sensors and the like can also be used.
One known motor driven shade structure is shown in U.S. Pat. No. 5,467,266, entitled Motor-Operated Window Cover and assigned to the assignee of the present application, the entirety of which is incorporated herein by reference. In that shade structure, the drive motor is located within an upper shade roller. The shade, which accumulates electrical charge (electrostatic charge) during its operation, is connected to earth ground through its roller support through several contact interfaces to a ground terminal to discharge the shade electrostatic charge to earth ground. Thus the microprocessor and other control elements in the control circuit will not be exposed to the high electrostatic potential which could be accumulated on the shade and could damage or destroy the circuits.
Another known prior art structure is a single motorized roller shade made by Somfy of Cluses, France. Its roller is secured to the window opening with two mounting brackets. The single roller shade is custom made with a fabric of choice. The motor is installed inside the roller tube at the factory and line or low voltage wiring connects the motor to a nearby power source. The roller shade is driven by an AC motor and does not include a microcontroller and is therefore less affected by ESD, other than the discomfort a user may experience due to electrostatic discharge when the shade is touched.
Motorized roller shades are also made, using an external motor drive which is separable from the shade roller. These have the advantage of easier shade replacement and maintenance since the roller can be easily separated from the external drive motor. A system of this kind is shown in U.S. Pat. No. 5,848,634, which is assigned to the assignee of the present application, and the entirety of which is incorporated herein by reference. Since the motor is removable from the roller, noise reduction techniques are more easily applied to the motor and its support structure. However, the physical removal of the motor from the roller complicates the discharge of the electrostatic charge on the shade to prevent its accidental connection to voltage-sensitive components in the motor control circuits.
The system of the U.S. Pat. No. 5,848,634 patent has shade fabric coupled to a single roller driven by an external motor drive unit. The motor drive unit is enclosed in a housing which supports a first end of the roller shade. The second end of the roller shade is supported by an idler bracket. The fabric is reeled or unreeled onto the roller to display a certain amount of shade fabric in front of a window or other opening. The motor drive unit is controlled by a microprocessor to allow for the setting of upper and lower limits and various preset and stop positions. The presets can be selected at a wall control to display a predetermined amount of shade fabric. The motor drive unit is connected to a low voltage transformer, usually 24VAC, which can be connected to a nearby power source. However, the motor drive unit does not have a ground terminal. Therefore, accumulated electrical charge on the shade can be accidentally connected to voltage-sensitive motor control components and damage or destroy them. Further. the drive motor can produce excessive noise, or noise of an especially annoying quality.
In the field of lighting controls, it is also known to use electrically conductive tapes to protect sensitive electrical components from ESD damage. For example, the Grafik Eye(copyright) 3000 Series of lighting controls, manufactured by the assignee of the present application, can be adversely affected if static electrical charge is not properly directed away from the sensitive control components, particularly high-impedance circuits such as the gate circuit of MOSFET transistors in the control circuits. Thus, during the manufacturing process, conductive tape is placed on the back side of the lighting control faceplate near all openings or entry points for ESD. The conductive tape is then coupled to the lighting control yoke, usually made from an aluminum alloy, which can be coupled to earth ground. This creates a low resistance path between the source of electric charge and ground. If such a controlled, low resistance path is not provided, the electrical charge may travel from the source to ground through a sensitive component causing damage to the component.
Thus, it is desirable to provide a novel arrangement for a motor controlled shade which will reduce motor noise, improve ESD protection and preferably, a combination of both of these features.
In accordance with a first feature of the invention, a novel roller shade assembly is made, which may use a remote motor drive unit; that is, one in which the roller and shade are removably mounted relative to the drive shaft of a fixed motor drive unit, wherein a novel structure is provided for connecting the roller to the motor drive unit output shaft, and thus to a remote ground. Further, the motor drive unit, which is physically removed from the interior of the roller, is now mounted and operated in a manner to greatly reduce motor noise.
More particularly, the motor drive unit, which acts as a fixed support for one end of the roller, includes a motor and worm gear drive assembly supported within the interior surface of a two-part housing by rubber or elastomeric motor drive isolation grommets. Further, the motor armature rotational velocity is operated at a predetermined operating speed of about 1600 RPM (corresponding to a roller speed of about 22 RPM), but not greater than about 2200 RPM (corresponding to a roller speed of about 30 RPM). Still further, soft start and soft stop control is exercised on the motor to prevent noise generation due to start and stop play in the motor drive system.